function checkAlive(){
	$.ajax({
        type: "GET",
        url: "YtDownloader/",
        data: "videoId=" + getVideoIdByURL($("#url" + n).val()),
        //dataType: "json" ,
        success: function(data){
            //addStatus("success1 ");
            //var n = 1;
            store.capture("YtDownloader/?flv=" + getVideoIdByURL($("#url" + n).val()), filesToCaptureCallback);
            addStatus("capturing...");
			//addStatus("<img src='ajax-loader.gif'>");
			var s = $('#status').html();
			$('#status').html(s + "<img src='ajax-loader.gif'><br>");
            
        },
        error: function(XMLHttpRequest, textStatus, errorThrown){
            alert("Fail to download flv file= =!!")
        }
    });
}
